A. Field of the Invention
The invention relates to the field of synthesizing video material, particularly with a view to enhancing a three dimensional appearance of that material.
B. Related Art
Synthesizing the image of a 3-D scene, as it would be captured by a camera from an arbitrary viewpoint, is a well-known research problem and several different approaches have been proposed. Given a complete 3-D model, it is possible to render the scene from any viewpoint. Rendering techniques are well known in the field of Computer Graphics (as described, for example, in J. D. Foley, A. van Damm, S. K. Feiner, and J. F. Hughes, “Computer Graphics-Principles and Practice”, Addison Wesley, Second Edition, 1992, Chapter 14). However, generation of the model is a tedious, error-prone and labor intensive task.
On the other hand, some researchers have tried to infer 3-D information directly from images. Various methods have been developed for recovering both the shapes of the objects and the camera motion from a sequence of images (for example, O. Faugeras, “Three-Dimensional Computer Vision: a Geometric Viewpoint”, MIT press, 1993). These methods are typically computationally intensive. Furthermore, in many cases the input sequence had been captured by a pan-tilt-zoom camera, preventing recovery of the 3D model of the scene.
Another approach is to perform image based rendering (as in L. MacMillan: “An Image Based Approach to Three-Dimensional Computer Graphics”, Ph.D. dissertation, University of North Carolina, 1997), in which case no explicit 3-D model of the object and the environment is required. These methods avoid reasoning in 3-D by using projective constraints and invariants.